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MG MGB GT V8 Factory Originals Technical - Can you put a T5 on a 1.8?

I may be in the wrong area but I was wondering if it is possible to put a T5 into a standard "B" and mate it up to the 1.8L engine. If you look at the best scenario to turbocharge an engine, the standard "B" is a great candidate. The pre-requisites for a good engine are:

Compression ratio 8.0 or lower
Forged Crankshaft
Iron Cylinder Head (Good Sealing, no Flex)

This engine should easily handle 14 psi. boost which would put it way ahead of the V8 conversion in both torque and horsepower output. Consider the math...if you boost to 14.7 psi you have effectively doubled the size, and output, of the engine. Basically you have a 3.6L vs. 2.5L argument.

I just can't see going to the trouble (and expense) of putting a V8 into the car when the other option is incredibly cheap. I can boost the engine for under $100.00 using a junkyard turbo and a smog pump pre-spooler to eliminate lag. I have a plasma cutter, TIG welder and exhaust tubing machines on hand.

The only problem I see is the transmission. This tranny won't handle the 170+ horsepower output. Has this been done before and what has the solution been.

I don't intend to denegrate the V8 conversion. It is real cool and if I had the money and time, I'd do it. There is just a much cheaper/easier option.

Thanks for any help,

John Wagner
73' MGB-GT
John Wagner

I'd probably just use a Nissan 5-speed box ... guys like Towery can supply the bellhousing etc. I dunno where you'd get a bellhousing for a T5 mated to an 1800.

As to the motor, are you going to strengthen it, at least doing stuff like using ARP studs to hold the head down? I can see it grenading right quick, that's all.

If you do this, please keep us posted on how you do it. Here are the things I would see as possible difficulties:

1. Where are you going to put the turbo? The only way to keep the extreme heat from the intake would be to use a crossflow head.
2. What are you planning on doing for fuel management? Turbos + carbs = real pain in the rear. Need fuel injection!
3. I don't have any idea what a turbo pre-spooler is...
4. You would have to be really good at measurements and machining, or you will have to purchase an adaptor for your trans of choice.
5. Stock head flow on the MG sucks...really bad!!!

If you are trying to do a conversion on a budget, I am almost finished installing a 2.3 turbo Ford in my MG. Total investment so far was $300 for a parts TurboCoupe with a T-5, and then a Volvo intercooler for $50 from the junkyard...with bypass valve. Conversion kit has been supplied by the Lincoln Electric Company. If you would like any pictures, I can send you what I have done, along with some pictures from someone who has completed it.
G.P. Copes

John, if you don't mind me asking, how much money do you plan on spending? As a genereal rule, whenever starting from scratch, I would always budget more time and money than I believe necessary. As G.P points out, you'll need to do some fancy routing to keep the carbs away from all that heat. Are you planning a draw-through or blow-through carb setup? If blowthrough, you'll need a pressure box or modify carbs. You'll need an intercooler if you plan on 15 psi and those stock pistons/head gasket/etc will probably not last very long. Hopefully your radiator will handle the extra horsepower. You'll need a custom driveshaft. If I were you, I would keep the stock tranny and see how it holds up. Also, because of required ignition retard, heat transfer and higher cylinder pressures, 14.7 psi won't double your horespower or torque- more likely about 17-20 psi would do it. Also consider that your boost will come in progressivly and will be safer for your tranny, rear end etc. Most V8 conversions will have absolutely brutal torque right off idle. I wish you luck on the project though, and please keep us updated.

Hi Everyone,

I plan on routing the exhaust over to the passenger side of the engine. What the heck...If IMSA cars can run the turbo at the rear of the car I can certainly handle three feet of exhaust pipe without much loss. I plan on running a draw through design as a blow through would be too much of a pain with SU's. A pre-spooler will be made out of the biggest smog pump I can find. A pump off of a big block GM will blow a lot of air, especially with a smaller pulley. I will pump the air into an orifice drilled into the exhaust side of the turbo to have boost present, even at idle. As far as carb vs. fuel injection goes....the argument is a moot point. Why spend money to regulate fuel delivery when a draw through, properly set up, does it for you. I already have several Weber sidedrafts on my garage shelf. Since I already have plenty of parts on hand for this project, it shouldn't take me more than a couple hundred bucks max. Fortunately I am a stay-at-home dad, with kids almost ready to go back to school. Plenty of time + plenty of tools + plenty of spare parts = Fast Boost. I probably won't start the project until mid August when school is back in session. I'll keep you all informed as to it's progress and adaptability. I'll attempt to convert it for as little money and with as little specialty fabrication as possible. What the heck...we're all in this together. If I keep boost relatively low and control the fuel ratio/vacuum advance the engine should last a long time. Power doesn't kill boosted engines....detonation does. Are the pistons in the standard "B" engine prone to failure?

Thanks Y'all
John Wagner
John Wagner

How does the t-5 feel compared to the stock b? ive heard horror stories about sloppy shifting t-5's. i just love the way my cut down shifter feels
Ben Davids

T-5s feel fine. I have a Rover 5-speed only because it was there for the asking. No need to worry about either with a normally-aspirated 1800 though. Your stock B tranny would have a life expectancy measurable in nanoseconds behind a good turbo setup.

Ben, I find that stock shifters due tend to get sloppy and many a times I have missed third gear under racing situations. Luckily there are vast amount of shifters for the t-5 in the aftermarket that really increase the firmness.

I like my T5 shifting, though I will likely get a aftermarket shifter to shorten it up and posible help fitment in my shifter boot.

Just some food for thought:
The loosness is probably because of the $1.00 "cup bushing" that is in a stock T5 system. It goes between the shift lever and the linkage, and acts like a wear buffer so that rather than having metal on metal you have a synthetic piece to absorb some shock and all the wear.. When it gets wornk,it gets sloppy.. They are not "easy" to find, call your local tranny shops, eventually you will find one that knows what you are talking about, FYI it is NOT the bussing in the shift lever but goes between the lever and the linkage rod. I can try to get a part number but it may be a bit as I moved my computer room and files are everywere...

As for the T5's being weak, you need to take into consideration many people in the big muscle cars don't shift them "properly" they are running them hard, and have much heavier cars, with much more torque.. A 3600+lb car with 350ft/lbs of torque will put stress on a tranny that is probably many TIMES the stress our 2400lbs cars with <=300ft/lbs of torque (V8 car) will ever produce.. Couple that with "slam shifting without using the clutch and Kaboom, you have tranny pieces all over the road..
Larry Embrey

Interesting you should bring this up. When I was starting a V6 conversion on a GT, I happended to compare the T-5 to a MGB engine and tranny I had just pulled out. I didn't make any exacting measurements, but a little caliper and ruler work at the time made me think that all that would be required would be an engine adaptor plate and a custom pilot bushing. The key was that the T5 pilot nose was small enough to go into the MGB crank, and the input shaft length was close to ideal to allow use of a 1/4 or 3/8 inch thick adapter plate. The fact that the MG uses a rear engine plate would make it really simple to fab. If I remember, it looked like a combination of a T5 throwout bearing with a stock clutch would come close to working. An internal hydraulic throwout with a built in adjuster may be just the ticket. Anyway, it looked like it would be a lot cheaper than some of the $1500 5speed kits running around.
Arthur Shaffer

Hi Everyone,

Thanks for all of the input. One post mentioned an adapter being available from "Towery" for a Nissan 5spd gearbox. I can't seem to find any information on these folks. Does anybody have a URL on them or a "snail mail" address? I would love to save myself the trouble of fabricating an adapter.


John Wagner
MGB-GT 73'
John Wagner

Glen Towery's phone number is 302-734-1243, or Towery Foreign Cars, P.O. Box 354, Cheswold, DE. 19936.
Joe Ullman

This thread was discussed between 23/07/2002 and 30/07/2002

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